UPDATE: This morning I started charging the M3 and monitored it via the app about every 3-5 minutes. It started out fine at 48 amps and 44-45 miles of range per hour. It dropped down to 24 amps at about the 55 minute mark. At that point, I looked at the display and there was a message: "Charging speed reduced High temperature detected by Wall Connector" (pictures attached) which confirms the theory made by several of you. Never saw that message before, but never looked at the display immediately after the drop off happened either.
I have found a post on another forum that had this same problem with a new M3. But he also already owned another M3 and this problem is non-existent with that car which implies the problem is with the car. But found several other posts where the problem was with the wiring or wall charger (loose wires, low gauge). I have a friend nearby with a MS. I'm going to charge his car on my charger to see if his car experiences the same thing. If it does, then it's not the car and I will bring in my electrician to look at things. If his car charges OK with no drop off, then I will call Tesla for a service appointment. I'll update here as I find out more. Thanks everyone.
I have found a post on another forum that had this same problem with a new M3. But he also already owned another M3 and this problem is non-existent with that car which implies the problem is with the car. But found several other posts where the problem was with the wiring or wall charger (loose wires, low gauge). I have a friend nearby with a MS. I'm going to charge his car on my charger to see if his car experiences the same thing. If it does, then it's not the car and I will bring in my electrician to look at things. If his car charges OK with no drop off, then I will call Tesla for a service appointment. I'll update here as I find out more. Thanks everyone.